England is home to four kinds of wild snake, not three as was previously believed, according to scientists.

The barred grass snake, Natrix helvetica, is now recognised as a species in its own right distinct from the common or eastern grass snake (Natrix natrix).

Both snakes can be found in lowland areas of southern England.

Unlike the adder (Vipera berus), neither creature is venomous.

The only other British snake, the smooth snake (Coronella austriaca), is also non-venomous and extremely rare.

Grass snakes, which grow to more than a metre (3ft) in length, live near water mainly feeding on amphibians such as frogs, toads and newts.

A corn snake

The barred grass snake is greyer in colour than its olive green cousin and lacks its most striking feature, a bright yellow collar.

Along the body are dark bands that are much more pronounced than they are in the common grass snake.

It used to be thought there was just one overall species of grass snake plus a number of subspecies that varied in appearance.

Professor Uwe Fritz, from the Senckenberg Research Institute in Germany, who led the international team of researchers, said: "We studied two areas where different genetic lineages of the grass snake come into contact.

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The discovery, described in the journal Scientific Reports, could have implications for grass snake conservation, said the researchers.

In the UK, the grass snake is protected under the Wildlife and Countryside Act, making it a criminal offence to injure or kill the animals.

"We now have to pay close attention to which species of grass snake is involved in each case, in order to be able to assess whether one of them may be more threatened than previously thought," said Prof Fritz.